I. Atoms are the smallest forms

– All matter is made of atoms• Chemists know about 100 basic elements

– Some exist individually– Some combine to make new substances

– Atoms in Earth’s crust and living things• 90% of the universe is composed of Hydrogen (H)

– H makes up 1% of the Earth’s crust– Most are combined with Oxygen (O) in the form of water

I. Atoms are the smallest forms• Most living things contain 25 types of atoms.• Most made of four types of atoms

– Oxygen (O)– Carbon (C)– Hydrogen (H)– Nitrogen (N)

– Names and Symbols of Elements• Each element has a unique name and symbol

– Some use the first letter of their name– Others have the first letter plus one other.

• If there is one letter to represent, it will always be capitalized• If two letters, second one is always lower cased.• Many names derived from Latin, Greek or other names.

I. Atoms are the smallest forms– Each element is made of different atoms

• John Dalton thought that each element was made of tiny particles called atoms.

• He stated that each atom of the same type is identical. Atoms of different kinds do not resemble any other type.

• Later discoveries indicated that the atom was broken down in to even smaller parts.

I. Atoms are the smallest forms– Structure of an atom

• Atoms are composed of three types of particles• Two are located within the center of the atom

called the nucleus.– Proton-positively charged particle– Neutron- neutral particle– Neutral particles are necessary to prevent all the “+”

charges from repelling each other and causing the nucleus to become unstable.

– Outside the nucleus are electrons- negatively charged particles

I. Atoms are the smallest forms• Electrons are much smaller in size than protons or

neutrons.• Electrons move so quickly around the nucleus that

they create a cloud around the nucleus.• Electrons are attracted to the nucleus because of

their negative charge and the protons positive charge inside the nucleus

I. Atoms are the smallest forms– Atomic numbers

• Atoms are determined by the number of protons in the nucleus.

• This creates the atomic number– Atomic Mass numbers

• The total of the protons and neutrons together give the atom’s atomic mass number.

I. Atoms are the smallest forms• Not all atoms of an element have the same atomic

mass – Atom will have the same number of protons– But not the same number of neutrons

• This creates an Isotope– Atoms of the same element that have different number of

neutrons– Some elements have many isotopes, others have just a few.

• Isotopes are designated by the name of the element and the total number of its protons and neutrons.

• You can find number of neutrons by subtracting atomic number from Atomic Mass Unit.

I. Atoms are the smallest forms– Atoms Form Ions

• An atom has the same number of protons and electrons.

• Each positive charge cancels out a negative charge.• There will be no overall charge• An Ion is formed when an atom gains or loses an

electrons– When electrons are lost, there are more protons giving an

overall positive charge– If electrons are gained, there are more electrons giving an

overall negative charge.

I. Atoms are the smallest forms• Formation of Positive ions

– When electrons lost, less repulsion of remaining electrons

– Positive ion is smaller than the neutral atom– Represent an ion using the chemical symbol and how

many electrons have been lost.– Write as a superscript Ca+2

I. Atoms are the smallest forms• Formation of Negative Ions

– When electrons gained, more are now there– Negative ion is larger then neutral atom– Extra electrons cause expanding of electron cloud– Represent using the chemical symbol with a negative

subscript and number gained– Cl-

– O2-

II. Elements make up the periodic table

– Elements can be organized by similarities• One way is by mass of atoms• Atomic mass of atoms is the average mass of all the

element’s isotopes– Mendeleev’s Periodic Table

• Organized elements based on properties• Based on physical and chemical similarities.• Created the periodic table where the rows increased in

atomic mass– Predicting New Elements

• Mendeleev left spaces where nothing known fit• Predicted new elements would complete the chart

II. Elements make up the periodic table

– Periodic table• Modern table has elements with similar properties

in columns• Elements arranged by atomic number, not by

atomic mass– Reading Periodic Table

• Each square tells specific information• Top number is the Atomic Number

– Number of Protons– Located in nucleus

II. Elements make up the periodic table

• Chemical symbol in the Middle– is the abbreviation of the element’s name– Contains one or two letters– Some are three letters b/c they are not yet named

• The element’s name. Written below symbol• Atomic mass. Number below name. Atomic mass

is all the isotopes of the element.

II. Elements make up the periodic table

• Element’s color indicates existence at room temperature.

– White means gas– Blue means liquid– Black means solid

• Background color indicates type of metal– Metal– Non metal– Metalloid

II. Elements make up the periodic table

– Groups and Periods• Elements arranged in a column

– Called a group– Labeled at the top of the column– Sometimes called a family

• Horizontal rows – called Periods– Properties of elements change predictably from one end

to the other.

II. Elements make up the periodic table

– Trends in Periodic Table• Atoms on left side of table form positive ions easily

(give away electrons for an overall positive charge)– Group 1 lose an electron to become +1 Ions– Group 2 loses two electrons to become +2 ions– Group 18 do not form ions at all – Group 17 gain an electron to become negative ions– Group 16 can gain 2 electrons to become -2 ions– Groups 3 to 12 all form positive ions but the charge can

vary

II. Elements make up the periodic table

• Sizes of atoms vary across periods within groups. Important because it affects how the atom will react with another atom

• Densities follow a pattern– Generally increase from top to bottom– Elements within a period the left and right sides are least

dense,

• Middle is most dense

III. Periodic table is a map of the elements

– Distinct regions on the periodic table• Three main regions

– Metals on the left– Non metals on the right (except for Hydrogen)– Metalloids in the middle.

» Yellow box will indicate metal» Green nonmetal» Purple metalloid

• Location also indicate reactivity– Groups 1 and 17 most reactive– 18 least because they are stable.

III. Periodic table is a map of the elements

– Most Elements are metals• Conduct electricity and heat• Have a shiny appearance• Easily shaped (malleable) into

– Wire,– Sheets– Bent

• Exception is mercury , but all others a solids at room temperature

III. Periodic table is a map of the elements

– Reactive Metals• Group 1

– Called alkali metals– Very reactive

» Potassium» sodium

• Group 2 are alkaline earth metals– Less reactive than alkali– More reactive then most.

» Calcium» magnesium

III. Periodic table is a map of the elements

• Transition Metals– Groups 3-12– Generally less reactive– Found in foods we eat

» Copper,» Gold» Silver» Iron

• Rare Earth Metals– Located in top row of the two rows of metals– Referred to as Lanthanides– Called this because were once rare– Now only hard to isolate

III. Periodic table is a map of the elements

– Nonmetals and metalloids• Elements on right side are the nonmetals

– Opposite properties of metals– Mostly gasses

» Air is made of nonmetals» Carbon in living things

• Halogens– Elements in group 17– Means forming salts– Very reactive– Used to kill harmful microorganisms

III. Periodic table is a map of the elements

• Noble gasses– Group 18– Inert or unreactive

• Metalloids– Elements having both metal and nonmetal properties.– Located on either side of the zigzag of table

III. Periodic table is a map of the elements

– Atoms changing identity• Chemical reactions do not effect the nucleus of an atom• Certain conditions can change the number of protons• Each atom has isotopes with different numbers of

neutrons• Stability of nucleus depends on the right number of

protons and neutrons• Too few or too many neutrons, nucleus becomes

unstable• When this happens particles are produced from the

nucleus to restore balance

III. Periodic table is a map of the elements

• This change is accompanied by a release of energy

– Marie Curie named this process radioactivity.– She was first person to isolate polonium and radium

• Isotope is radioactive if nucleus has too many or too few neutrons

– Rare for small atoms– Heaviest elements (beyond bismuth, al isotopes are

radioactive

III. Periodic table is a map of the elements

• Measure radioactivity with Geiger counter– Detects particles from the breakup of the atomic nucleus

with clicks– More clicks more particles being produced

– Uses of Radioactivity in Medicine• Used to destroy tumors• Monitor activity of certain organs in body• Large/prolong exposure can do damage.